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Aviation History
1963
1963 - 0379.PDF
FLIGHT International, 14 March 1963 361 Whitworth Gloster 681 AS was intimated last week, the Minister of Aviation, Mr Julian Amery, announced on March 5 that RAF Transport Command is to replace its ageing Beverley and Hastings aircraft with an entirely new type—the Whitworth Gloster 681. The Air Staff formulated Operational Requirement 351 at least 18 months ago, and the advent of the high-efficiency turbofan, vec- tored-thrust propulsion engines, packages of lightweight lift units, flap blowing, blind landing and other technological advances enabled the requirement to call for a vehicle more capable and versatile than any previous transport aircraft. The same advances have enabled the British aircraft industry— and, it is fair to add, only the British aircraft industry—to exceed the OR.351 demands by a wide margin. At the same time, hard ware of this character is very expensive to develop. As long ago as last March 28 Interavia Air Letter reported "The requirement would be for 30 aircraft, but R & D and production for aircraft such as the BAC.208 or the AW.681 would cost about £100m . . ." Reluctance to spend such a sum, when an STOL Belfast or Lock heed C-130 could be bought very much more cheaply, appears to have been the principal reason for the prolonged delay in coming to a decision. It is immensely encouraging to record that the Government's decision is to produce the aircraft that the RAF has held out for. Like butter and certain brands of cigarette "it costs a little bit more," but the rewards for the extra outlay will be incalculable. If the programme is pressed forward to completion, it will not only provide tremendous moral and financial benefits across a wide section of British industry but will also result in an aircraft having unique capabilities in many military and certain civil fields. These capabilities can be briefly outlined in the following terms. The Whitworth Gloster 681 should be able to carry practically all military stores except for battle tanks, certain large radars not designed for airlifting and one or two specialist vehicles such as 30-ton tugs and trailers. It should be able to carry about 100 troops and their equipment, or 60 to 70 stretchers or 40,0001b or so of general freight. It should then be able to take off from any normal airfield, fly at least 1,500 miles at 500kt and land on a short forward airstrip. In a ferrying mission between airfields it should be able to fly 4,000 miles without air refuelling. Finally, when the occasion demanded, it should be able to take a load of some 25,0001b out of an airfield and set it down vertically in a forest clearing or any other reasonably flat and level area big enough to get the aircraft into. And, of course, it could lift itself out again (it is not possible to deduce whether the RAF wish it to do this with a substantial payload) and return to civilization. The configuration is the logical one predicted last week. A 707- type layout would have been lighter, but less suitable for either jet lift or the transport of vehicles and bulky stores. Main powerplants will be four vectored-thrust turbofans of about 15,0001b apiece. The Bristol Siddeley Pegasus is an obvious candidate, and could be bought off the shelf. At the same time, notice must be taken of the Rolls-Royce Spey, which could be provided either with a single rotary-cascade deflector or with plenum-chamber burning and either two or four rotating nozzles. For VTOL, fixed underwing pods of lift units would also be required. The first choice of lift unit is probably the Rolls-Royce RB.162, but the BS.59 lift fan is being developed specifically for VTOL transport application. Rolls-Royce are against vectored-thrust main engines. Their view, expressed in a recent SAE paper, is that, if the engines of a transport aircraft are suitably located "it would be advantageous to deflect the available thrust for take-off. However, it is debatable if it is economic to deflect through as much as 90°; there is less complication and less weight penalty if the gas flow is deflected through say 30° to 40°." This does not apply to the Pegasus, which can deflect to any angle without additional penalty. Whitworth Gloster have already gained extensive theoretical experience with studies into V/STOL versions of the Argosy and the Noratlas, the latter study being MoA-financed and being undertaken in conjunction with Short Bros & Harland. The same two companies will now work together on the 681, for "a substantial share of the production work" is being subcontracted to Belfast. An indication of the amount of new business which this pro gramme should bring to accessory manufacturers is provided by the fact that, in addition to comprehensive pressurization, blind- landing, autopilot, powered-controls, communication and navi gation and special role equipment, the 681 will require all the auto matic controls needed by any multiple jet-lift system as well as a conventional high-lift system plus controls for use at low forward speeds or in hovering flight. In our February 28 issue an article by a senior executive of E-A Flight Automation Ltd discussed the auto matic control systems needed by various types of jet-lift aircraft. Apart from drawing attention to the magnitude of the problems involved, this article also served to emphasize the degree to which the industry has anticipated the 681 by working on systems for it in advance; for example, one illustration showed an autostabilizer package for such an aircraft. Blowing and Controlling For STOL operations it is possible that the flaps will be blown; and this may even be extended to the control surfaces, for there should be ample air-bleed available during airfield operations. For flight at very low speeds with jet-lift pods, control might be effected by bleed-air jets at the wing tips and tail and/or nose. On balance, however, it appears more efficient to effect control about all three axes by deflecting or differentially varying jet thrust. Control in pitch could be effected by differential variation of the thrust between the front and rear units in each lift pod, while yaw control could be effected by differential tilt of some lift units or differential rotation of port and starboard main nozzles. Earlier in this account reference was made to national reluctance to undertake an R & D programme of such magnitude in order to produce only a handful of production aircraft. This has long been a fundamental handicap to most British military aircraft and weapon programmes, and the Government have tried to solve it by bringing in other nations to share the R&D costs. The NATO BMR-4 competition called for a much smaller aircraft than that which the RAF need, and the range specifications are utterly different. The United States, however, needs a machine exactly like the 681. Nobody today would be naive enough to imagine that the USA would ever buy military equipment on a massive scale that was not home-produced. So far as we are aware, no tangible result has been reached in any discussions between the two nations concerning aircraft in this class, although there may well have been such inter changes at both Government and industry level. The first 681 is unlikely to fly for about three years, but it would be deplorable if American pride rendered a co-operative programme impossible.. As we commented last week, it should at least be possible to find a. common standard of pallet and freight-handling system.
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